This invention relates to the use of organosilicate resins as hardmasks, etchstops, antireflective layers, adhesion promotion layers, chemical/mechanical polishing (CMP) stop layers, or other layers and combinations of layers in the fabrication of microelectronic devices, to a method of fabricating such devices, and to the resulting electronic devices.
The microelectronics fabrication industry is moving toward smaller geometries in its devices to enable lower power consumption and faster device speeds. As the conductor lines become finer and more closely packed, the requirements of the dielectrics between such conductors become more stringent. New materials having a lower dielectric constant than the dielectric constant for silicon dioxide, the traditionally used dielectric material, are being investigated. Among the lower dielectric materials that are attaining increased acceptance are spin-on, organic, inorganic or hybrid polymers having a dielectric constant of less than about 3.0. Polyarylenes, including polyarylene ethers and SiLK™ semiconductor dielectrics (from The Dow Chemical Company), are the primary organic polymeric dielectrics being considered. Examples of suitable inorganic polymers and hybrid polymers include organic silicate glasses (OSG) and carbon doped oxide (CDO) polymers, disclosed in U.S. Pat. Nos. 6,159,871 and 6,541,398, and elsewhere.
The fabrication of microelectronic devices using these new dielectric materials has been reviewed, for example, in, Material Research Societv Bulletin, vol. 22, no. 10 (1997). To date, however, the polyarylene dielectrics generally have been patterned in the traditional manner using inorganic hardmasks to transform the patterns into dielectric materials of the desired design. Typically, the polyarylene dielectric is applied to the substrate and cured, followed by Plasma Enhanced Chemical Vapor Deposition of an inorganic hardmask Deposition conditions must be carefully monitored to assure adequate adhesion between the hardmask and the polyarylene films. A pattern is formed in the inorganic hardmask according to standard patterning practices, for example, application of a photoresist or softmask, followed by exposure and development of the softmask, pattern transfer from the softmask into the hardmask, and removal of the softmask. Etching of the hardmask is typically done using fluorine containing compounds that generate fluorine reactive species in the reactive ion plasma. The underlying polyarylene dielectric can then be patterned using a different etching compound that typically does not contain fluorine.
Additional publications that discuss various methods and embodiments of dielectric materials, etch stops and hardmasks in fabrication of microelectronic devices include WO01/18861, which states that layers used as adjacent etchstop and dielectric materials should have substantially different etch selectivity's. The publication also teaches that an inorganic layer (defined as one containing no carbon atoms) should be used at a via level and metal level intermetal dielectric, and an organic, low dielectric constant, material should be used between the inorganic layers as an etch stop material.
WO00/75979teaches a structure having a first dielectric layer which is an organic polymer and a second dielectric layer over the first layer which is an organohydridosiloxane. U.S. Pat. No. 6,218,078 teaches the use of a spin on hardmask composition (a hydrogensilsesquioxane) which is coated over a low dielectric constant polymer (benzocyclobutene). U.S. Pat. No. 6,218,317 teaches use of methylated oxide hardmasks over polymeric interlayer dielectric (ILD) materials. Advantageously, both hardmask and ILD formulations can be applied by spin-coating techniques.
Organosilicate resins include fully hydrolyzed or partially hydrolyzed reaction products of substituted alkoxysilanes or substituted acyloxysilanes, as disclosed for example in U.S. Pat. No. 5,994,489 and WO00/11096. WO02/16477 teaches an organosilicate composition that is usefully employed as a hardmask in the fabrication of electronic devices. More particularly this composition comprises:
(a) an alkoxy or acyloxy silane having at least one group containing ethylenic instauration which group is bonded to the silicon atom,
(b) an alkoxy or acyloxy silane having at least one group containing an aromatic ring which group is bonded to the silicon atom, and
(c) optionally an alkoxy or acyloxy silane having at least one group which is a C1-C6 allyl, which is bonded to the silicon atom. An acid catalyst, such as hydrochloric acid could be included to enhance cure properties.
Disadvantageously, the foregoing composition is not curable excepting at elevated temperatures. This entails use of a heating step using a furnace or equivalent equipment. If an acid catalyst is included in the formulation the resulting composition possesses a limited “shelf life” or “pot life”. For this reason, the material must generally be retained at reduced temperatures (less than 20° C.) to prolong its useful life and avoid formation of particles and gels that can lead to defects in the applied film and difficulty in attaining a desired thin film thickness. This requirement for refrigeration imposes difficulties in shipping, storage, application, and subsequent use.
It would be desirable if a formulation having improved storage and use properties were available.